WASHINGTON (Reuters) – The U.S. Air Force has been secretly flying drones from a civilian airport in southern Ethiopia as part of an aggressive campaign against al Qaeda affiliates in Somalia and Yemen, the Washington Post reported on Sunday.

The paper said in its online edition that Washington has invested millions of dollars to upgrade a remote airfield in Arba Minch from where it was now flying a fleet of Reaper drones that can carry Hellfire missiles and satellite-guided bombs.

It quoted the Pentagon as saying the drones had been unarmed and had been used for surveillance and collecting intelligence only but that it would not rule out using them to launch lethal strikes in the future.

No one at the Pentagon was immediately available to comment.

The Ethiopian government denied the presence of any foreign military bases, the paper said, but added that U.S. military personnel and contractors had become increasingly visible in Arba Minch, a small city of 70,000 people.

Reapers, known as “hunter-killer” drones, have a range of about 1,115 miles (1,795 km) and Arba Minch is about 300 miles (480 km) south of the capital Addis Ababa.

Last month, the Washington Post reported that the United States was building a ring of secret drone bases in the Horn of Africa and the Arabian Peninsula. But it was not known where the Ethiopian base was or that it had become operational this year.